Was running along the same line. and as Usual things are a bit more complicated then MSDN let's you believe

The problem I'm not able to solve is if a form has zero controls that can recieve focus, in that scenario the usercontrole still will accept focus.
Normally you could concider to ignore that, but a form showing data that's locked by another user is typically a form with all controls set to Enabled = False

Code:
 Private Sub TextboxPlus_Enter(sender As Object, e As EventArgs) Handles Me.Enter
        If Not _enabled Then
            SelectNext(Me)
        End If

    End Sub

    Private Function SelectNext(Ctrl As Control) As Boolean

        Dim container As Control
        Dim result As Boolean

        container = Ctrl.Parent

        If container IsNot Nothing AndAlso Ctrl.Parent.Controls.Count > 1 Then

            'search on parent control
            For Each itm As Control In container.Controls

                If itm IsNot Ctrl Then
                    'don't bother to check already searched part of the tree
                    If itm.CanFocus Then
                        'ther is another control the paren that can focus
                        result = True
                        container.SelectNextControl(Ctrl, True, True, True, True)
                        Exit For
                    ElseIf itm.Controls.Count > 0 Then
                        'this control hold ome other controls... to investigate
                        If SelectNext(itm.Controls(0)) Then
                            result = True
                            Exit For
                        End If
                    End If
                End If
            Next
        End If

        If Not result AndAlso container.Parent IsNot Nothing Then
            result = SelectNext(container)
        End If


        Return result

    End Function